1. Technical Field
The present invention relates to an apparatus for inflating an inflatable vehicle occupant protection device.
2. Description of the Prior Art
An inflatable vehicle occupant protection device, such as an air bag, is deployed upon the occurrence of a vehicle crash. The air bag is part of a vehicle occupant protection apparatus which further includes a crash sensor and an inflator. The inflator includes a housing and an inflation fluid source, such as a solid propellant, in the housing. When the crash sensor senses a crash-indicating condition of at least a predetermined threshold level, the inflator is actuated and produces inflation fluid under pressure in the inflator housing. The pressurized inflation fluid is directed out of the inflator housing and inflates the air bag into the vehicle occupant compartment. When the air bag is deployed in this manner, it helps to protect an occupant of the vehicle from a forceful impact with parts of the vehicle as a result of the crash.
When the inflator is actuated at an elevated ambient temperature, the pressure of the inflation fluid in the inflator housing increases. An inflator must be strong enough structurally to contain these elevated pressures. If the pressure in the inflator housing is thus increased, the mass flow rate of the inflation fluid flowing into the air bag can increase above the desired flow rate. Also, the possibility of such increased pressures may make it unfeasible to use a solid propellant which has a high burn rate exponent, that is, a high sensitivity to pressure variation.
The present invention is an inflator for providing inflation fluid for inflating an inflatable vehicle occupant protection device. The inflator comprises a housing defining first and second combustion chambers. A first inflation fluid source in the first combustion chamber is actuatable to effect flow of inflation fluid to inflate the inflatable device. The inflator includes a first initiator in the housing for, when energized, effecting actuation of the first inflation fluid source. A second inflation fluid source in the second combustion chamber is actuatable to effect flow of inflation fluid to inflate the inflatable device. The inflator includes a second initiator in the housing for, when energized, effecting actuation of the second inflation fluid source.
The housing deforms due to the pressure of inflation fluid in the housing upon actuation of one or both of the inflation fluid sources. The housing, after deforming, has a fluid passage for directing flow of inflation fluid out of the housing to the inflatable device. The flow area of the fluid passage varies in accordance with the pressure of inflation fluid in the housing. The housing comprises first and second housing parts having a first condition in abutting engagement with each other and a second condition, after deformation of the housing, spaced apart from each other to define the fluid passage. The first housing part comprises a one-piece metal member that supports the first and second initiators and defines the combustion chambers.